In a known method and apparatus of this kind (DE 37 24 698 A1) a roughing grinding wheel has the form of an interchangeable grinding wheel which can be removed from the grinding spindle. This interchangeable grinding wheel has sections to break the edges of the cams during roughing. During the grinding procedure the roughing wheel is not displaced laterally, instead the cam contour is roughed by a single plunge cut prior to the interchangeable grinding wheel being removed. A different roughing wheel is required for each cam width or for each chamfer form. During roughing the contact surface between the grinding wheel and the workpiece is large, to which no coolant is able to find access. This results in the feed rate having to be kept relatively low since excessively increasing the feed rate or cutting volume per unit of time would heat up the workpiece too rapidly. This in turn produces grinding cracks in the surface or even a change in the structure of the workpiece which is, of course, not wanted. This known method of grinding can be employed only to a limited extent also with new materials finding increasing application, especially e.g. hard shell castings or materials exhibiting quite different properties when being machined that those normally used formerly.
U.S. Pat. No. 3,019,562 and JP Abstract 54-83195 also describe working with two grinding disks, the roughing being done with a roughing wheel having a cylindrical grinding surface and the outer surface of the cam then being finished by means of a separate finishing wheel once roughing has been completed after one or more rotations of the workpiece. Here too, the disadvantages involved excessive heating occurs as already mentioned in conjunction with DE 37 24 698 A1.